Temperature sensors of the type employing a resistance wire are generally well known in the art. However, problems have heretofore occurred with respect to the making of a temperature sensor within a portion thereof is like a spool carrying the resistance wire and more particularly where the resistance wire is in the form of a coil having, for example, 500 turns and being of relatively small cross-sectional diameter as, for example, 0.0015 inch.
In such prior art structures, it has been found that most had failed shortly after use had commenced. The failure always occurred in the resistance wire and was not limited to a fracture or break in only one "turn" or coil of the wire. Attempts to correct this, as by employing different materials of increased strength and/or altering the configuration of the spool-like portion, did not succede.
However, it has now been discovered that the cause of such resistance wire failure is due to the thermal expansion, of the spool-like portion, which causes the coiled resistance wire to experience mechanical radial expansion to the degree that a fracture (or fractures) occurs therein. It has also been discovered that such thermal expansion of the material forming the spool-like portion can be permitted, without causing a fracture in the coiled resistance wire, as long as the direction of such thermal expansion is permitted to occur not exclusively in the radial direction.
Accordingly, the invention as herein disclosed and claimed is primarily directed to the solution of the foregoing as well as other related and attendant problems.